Ruthenium‐Catalyzed Synthesis of Cyclic and Linear Acetals by the Combined Utilization of CO₂, H₂, and Biomass Derived Diols

Abstract

Herein a transition‐metal catalyst system for the selective synthesis of cyclic and linear acetals from the combined utilization of carbon dioxide, molecular hydrogen, and biomass derived diols is presented. Detailed investigations on the substrate scope enabled the selectivity of the reaction to be largely guided and demonstrated the possibility of integrating a broad variety of substrate molecules. This approach allowed a change between the favored formation of cyclic acetals and linear acetals, originating from the bridging of two diols with a carbon‐dioxide based methylene unit. This new synthesis option paves the way to novel fuels, solvents, or polymer building blocks, by the recently established “bio‐hybrid” approach of integrating renewable energy, carbon dioxide, and biomass in a direct catalytic transformation.

Utilization of Formic Acid as C1 Building Block for the Ruthenium‐Catalyzed Synthesis of Formaldehyde Surrogates

“…In previous work, an active molecular ruthenium catalyst, cooperating with Lewis acids towards flexible cascade transformations could be established . The versatile triphos‐based ruthenium catalyst [Ru(triphos)(tmm)] (triphos=1,1,1‐tris(diphenylphosphinomethyl)ethane, tmm=trimethylene methane) represents a robust hydrogenation catalyst, operating via a series of hydride transfer/protonolysis steps and allowing to activate CO 2 and challenging organic functionalities .…”

Catalytic Reductive Alcohol Etherifications with Carbonyl‐Based Compounds or CO2 and Related Transformations for the Synthesis of Ether Derivatives

“…In 2019, the group of Klankermayer reported the reductive etherification of a variety of biomass derived diols with CO 2 /H 2 for the sustainable construction of a larger family of linear and cyclic acetals using a similar procedure to the previously reported by themselves (Scheme 36). [211] Cyclic acetals such as 1,3‐dioxane or 1,3‐dioxepane are compounds of current significance presenting a wide range of chemical applications, such as their use as solvents. In addition, cyclic and linear acetals can be utilized as building blocks for the synthesis of polymers with high water solubility (polyoxymethylenes) and can be considered formaldehyde surrogates [212] .…”

“…In fact, if the formation of both cyclic/linear acetal is considered together, a combined TON of up to 622 could be reached, demonstrating the high efficiency of the process. [211] A variety of diols could be employed with a linear/cyclic selectivity depending on the number of carbon atoms between both hydroxy groups.…”

Challenges and Opportunities in the Production of Oxymethylene Dimethylether

“…, Interestingly, reacting CO 2 /H 2 and ethanol resulted in diethoxymethane which is identified as a promising fuel candidate “bio‐hybrid fuel” from a production perspective. , …”